1. Field of the Invention
This invention relates to link chains for power drives, and, in particular, to a link chain provided with a quarter or half-turn to increase its contact length. Accordingly, it is a general object of this invention to provide new and improved chains of such character.
2. Description of the Prior Art
An endless standard link chain can be driven by a sprocket wheel which causes the links of the chain to rest on surfaces at ninety degrees to the preceding and followings links, such surfaces being at 45.degree. to the plane of the sprocket. Such sprocket wheels are disclosed in the following U.S. Pat. Nos:
325,539--Herman; PA1 662,768--Crowe; PA1 2,101,685--Nisbet; PA1 3,415,135--Royer et al.; PA1 3,766,791--Huttinger; PA1 4,108,014--Schreyer et al. PA1 U.S. Pat. No. 234,444--Wexel PA1 U.S. Pat. No. 649,091--Williams PA1 U.S. Pat. No. 2,065,788--Biedermann PA1 U.S. Pat. No. 2,190,129--Stahl
In U.S. Pat. No. 3,934,407 to Lange, each chain link in succession is alternately rotated about its axis and erected to a vertical position for engagement by upsetting members and welding electrodes.
The following United States Patents all refer to curbing of chains which is performed by twisting individual links, though Williams discusses the twisting of the entire chain:
A band with a half twist has been described by August Mobius, a German mathematician, in his Werke, Volume II, 1858. The Mobius strip, or Mobius band, as it is called, is a one-sided surface that can be formed from a rectangular strip by rotating one end 180.degree. and attaching it to the other end (The American Heritage Dictionary of the English Language--1969).
A Mobius strip, being endless, edgeless and one-sided, can be the subject of intellectual discussion (see Scientific American, December 1968, pp. 112-115) and can have practical uses. As stated in the Scientific American article, Lee De Forest obtained U.S. Pat. No. 1,442,632 for Mobius filmstrip that records sound on both "sides". A similar concept was applied to tape recorders so that the twisted tape runs twice as long as it would otherwise. Several patents have been granted for Mobius strip conveyor belts designed to wear equally on both sides. U.S. Pat. No. 3,302,795 to J. W. Jacobs relates to a self-cleaning filter including an endless belt having a halftwist whereby one surface portion of the belt alternately faces away from a supply housing and toward a backwash housing. U.S. Pat. No. 3,267,406 to Richard L. Davis relates to a Mobius strip non-inductive resistor.
The prior art does not suggest the prolongation of the life of an endless standard link chain by providing it with a quarter-turn or half-turn twist for a chain having an odd number or an even number, respectively, of links. It is to be recognized that alternate links of an eighteen link chain are displaced an average of twenty degrees from each other. Similarly, alternate links of a twenty-five link chain are displaced an average of fifteen degrees from each other. Since intermediate links would be at approximate right angles thereto, it is appreciated that a Mobius "strip" does not simply suggest itself to a three dimensional chain.